Damping fluid pressure waves in a subterranean well

ABSTRACT

A system and method of damping fluid pressure waves in a subterranean well. In a described embodiment, pressure waves are damped by positioning a dampener in the well during a perforating operation. The dampener may attenuate the pressure waves by absorbing the pressure waves, flowing the pressure waves through viscously damping material, generating complementary pressure waves, changing a material phase, or by a combination of these methods.

BACKGROUND

[0001] The present invention relates generally to equipment utilized andoperations performed in conjunction with a subterranean well and, in anembodiment described herein, more particularly provides a system andmethod for damping fluid pressure waves in a subterranean well.

[0002] It is well known that detonation of perforating guns in a wellcan cause damage to equipment in the well. It has generally beenconsidered that this damage is due primarily to forces generated bydetonation of the perforating guns. These forces are transmitted toother equipment via a tubing string in which the perforating guns andthe other equipment are interconnected.

[0003] For this reason, previous attempts to protect the equipment fromdamage have focused on isolating the equipment from the forces generatedby the perforating guns' detonation. For example, shock absorbers havebeen interconnected in the tubing string between the equipment and theperforating guns. As another example, methods have been developedwherein the equipment is physically separated from the perforating gunsprior to detonating the perforating guns.

[0004] However, damage to equipment may actually, or additionally, becaused by pressure waves generated by the perforating guns when they aredetonated. Shock absorbers do not isolate the equipment from damage dueto these pressure waves. Furthermore, separating the equipment from theperforating guns may not be necessary if damage to the equipment may beprevented, or at least substantially reduced, by damping the pressurewaves.

[0005] Damping pressure waves may also be beneficial in other operationsperformed in wells. For example, fracturing operations,propellant-driven packer setting, casing repair, etc.

SUMMARY

[0006] In carrying out the principles of the present invention, inaccordance with embodiments thereof, a system and method of dampingfluid pressure waves in a subterranean well is provided. In a describedembodiment, pressure waves are damped by positioning a dampener in thewell during a perforating operation. The dampener may attenuate thepressure waves by absorbing the pressure waves, flowing the pressurewaves through viscously damping material, generating complementarypressure waves, changing a material phase, or by a combination of thesemethods.

[0007] In one aspect of the invention, a perforating system for asubterranean well is provided. The system includes a perforating gunpositioned in the well, and a fluid pressure wave dampener positioned inthe well, The dampener damps pressure waves generated by detonation ofthe perforating gun.

[0008] In another aspect of the invention, a method of damping pressurewaves in a subterranean well is provided. The method includes the stepsof: providing a fluid pressure wave dampener; positioning the dampenerin the well; generating the pressure waves in the well; and damping thepressure waves with the dampener.

[0009] These and other features, advantages, benefits and objects of thepresent invention will become apparent to one of ordinary skill in theart upon careful consideration of the detailed description ofrepresentative embodiments of the invention hereinbelow and theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a schematic cross-sectional view of a first methodembodying principles of the present invention;

[0011]FIG. 2 is a perspective view of a first pressure wave dampenerembodying principles of the invention;

[0012]FIG. 3 is a schematic cross-sectional view of the first pressurewave dampener;

[0013]FIG. 4 is a schematic cross-sectional view of a first alternateconstruction of the first pressure wave dampener;

[0014]FIG. 5 is a schematic cross-sectional view of a second alternateconstruction of the first pressure wave dampener;

[0015]FIG. 6 is a schematic cross-sectional view of a second pressurewave dampener embodying principles of the invention;

[0016]FIG. 7 is a schematic cross-sectional view of a third pressurewave dampener embodying principles of the invention;

[0017]FIG. 8 is a schematic cross-sectional view of a fourth pressurewave dampener embodying principles of the invention;

[0018]FIG. 9 is a perspective view of a fifth pressure wave dampenerembodying principles of the invention;

[0019]FIG. 10 is a side elevational view of the fifth pressure wavedampener.

[0020]FIG. 11 is a schematic cross-sectional view of a second methodembodying principles of the present invention; and

[0021]FIG. 12 is a schematic cross-sectional view of a third methodembodying principles of the present invention.

DETAILED DESCRIPTION

[0022] Representatively illustrated in FIG. 1 is a method 10 whichembodies principles of the present invention. In the followingdescription of the method 10 and other apparatus and methods describedherein, directional terms, such as “above”, “below”, “upper”, “lower”,etc., are used only for convenience in referring to the accompanyingdrawings. Additionally, it is to be understood that the variousembodiments of the present invention described herein may be utilized invarious orientations, such as inclined, inverted, horizontal, vertical,etc., and in various configurations, without departing from theprinciples of the present invention.

[0023] In the method 10, a tubing string 12 is conveyed into a wellbore14. The tubing string 12 includes a packer 16, a production valve 18, aperforating gun 20 and a firing head 22. The packer 16 is set in casing24 lining the wellbore 14, and the perforating gun 20 is detonated toform perforations 26 extending outwardly through the casing.

[0024] A bridge plug or sump packer 28 may be set in the casing 24 belowthe perforating gun 20 prior to, or in conjunction with, running thetubing string 12 into the well. Alternatively, the wellbore 14 below theperforating gun 20 may be open to the casing shoe (not shown) or thebottom of the well.

[0025] Any number of perforating guns, firing heads, etc. may be used inthe method 10 in keeping with the principles of the invention. It shouldalso be clearly understood that, although the method 10 as describedherein is a method wherein a perforating operation is performed, theprinciples of the invention are not limited to any particular details ofthe method described herein, and are not limited to perforatingoperations at all. The principles of the invention have application inany operation wherein it is desired to dampen pressure waves in a well,for example, formation fracturing operations, casing repair operations,packer setting, etc., each of which may generate damaging pressure wavesin the well.

[0026] It has been found that pressure waves generated by detonation ofa perforating gun, such as the perforating gun 20, travel through fluidin the well and create pressure differentials across equipment in thewell. For example, a pressure wave generated at the perforating gun 20will travel both upward and downward in the wellbore 14. Upwardlytraveling pressure waves will reflect off of the packer 16 and begin totravel downward. Downwardly traveling pressure waves will reflect off ofthe plug 28, or the bottom of the well, and begin to travel upward.

[0027] Where coinciding in-phase, or approximately in-phase, pressurewaves are at their maximum pressure amplitude, a relatively highpressure is experienced by the tubing string 12. This condition isbelieved to occur typically just below the packer 16, at the top end ofthe perforating gun 20, and just above the plug 28 or bottom of thewell.

[0028] Where coinciding in-phase, or approximately in-phase, pressurewaves are at their minimum pressure amplitude, a relatively low pressureis experienced by the tubing string 12. This condition is believed tooccur typically one-fourth wavelength above the plug 28 or bottom of thewell, one-fourth of the distance from the top end of the guns to theplug or bottom of the well, and one-fourth of the distance from thepacker to the plug or bottom of the well.

[0029] When the relatively high and low pressures are applied to thetubing string 12, the differential between the high and low pressuresproduces very high stresses in the tubing string, leading to significantdamage to the equipment interconnected therein. Therefore, in the method10, a pressure wave dampener 30 is interconnected in the tubing string12. The dampener 30 acts to reduce the amplitude of the pressure wavesgenerated in the well, thereby decreasing the pressure differentialproduced across the tubing string 12.

[0030] The dampener 30 may operate by absorbing or viscously damping thepressure waves, or by generating a resonant frequency which complementsthat of the pressure waves in the well. If the dampener 30 operates byabsorbing or viscously damping the pressure waves, it should preferablybe positioned at one or more locations where the highest fluid velocityis found, which is where the pressure wave amplitude is at its minimum,as described above. If the dampener 30 operates by generatingcomplementary pressure waves, it should preferably be positioned at oneor more locations where the lowest fluid velocity is found, which iswhere the pressure wave amplitude is at its maximum, as described above.

[0031] Referring additionally now to FIG. 2, a pressure wave dampener 32is representatively illustrated. The dampener 32 may be used for thedampener 30 in the method 10. However, it should be understood that thedampener 32 may be used in other methods, without departing from theprinciples of the invention.

[0032] The dampener 32 includes a pressure wave absorbent material 34enclosed in a protective outer cage 36. The pressure wave absorbentmaterial 34 is preferably a porous or fibrous material, such as steelwool, mineral wool, open-cell foam, etc. The material 34 viscouslydampens pressure waves by forcing the fluid to flow through its manysmall passages in order to transmit pressure therethrough.

[0033] Referring additionally now to FIG. 3, a cross-sectional view ofthe dampener 32 is representatively illustrated. In this view it may beseen that a hollow cavity 38 is formed within the material 34. Thecavity 38 is hollow in that it has none of the material 34 therein. Thesize (height, diameter, volume, etc.), shape and position of the cavity38 may be adjusted as desired to “tune” the dampener 32 so that itattenuates a particular pressure wave frequency. For example, it may befound through experimentation or practical observation that a particularfrequency band causes a substantial portion of damage to the tubularstring 12. In that case, the size of the cavity 38, or other parts ofthe dampener 32, may be adjusted to target that frequency band.

[0034] Note that interior and exterior surfaces 37, 39 of the material34 may be smooth, and/or may be provided with scallops, crenellations,fingers, peaks and valleys, other recesses, other projections etc., asdepicted in FIG. 3. These various surfaces may be used to target aparticular pressure wave frequency and/or increase the overallattenuation provided by the dampener 32.

[0035] Referring additionally now to FIG. 4, another alternateconstruction of the dampener 32 is representatively illustrated. In thisconstruction, a flow passage 40 of the tubing string 12 extends axiallythrough the dampener 32. The material 34 is isolated from the flowpassage 40. This construction enables production flow, equipment,circulation, etc., to pass through the dampener 32.

[0036] An annular cavity 42 may be provided in the material 34. As withthe cavity 38 described above, the size, shape and position of thiscavity 42 may be adjusted as desired to target a particular frequencyband for damping. As with the construction depicted in FIG. 3, theinterior and/or exterior surfaces 37, 39 of the material 34 may besmooth, and/or may be provided with scallops, crenellations, fingers,peaks and valleys, recesses, projections, etc.

[0037] Referring additionally now to FIG. 5, another alternateconstruction of the dampener 32 is representatively illustrated. In thisalternate construction, the material 34 is isolated from the cavity 38by a flexible impermeable membrane 44. The membrane 44 could, forexample, be made of an elastomer material, such as rubber, nitrile,viton, etc., or it could be made of a non-elastomer.

[0038] Preferably, the cavity 38 is filled with a liquid, such assilicone oil, etc. Alternatively, the cavity 38 could be in fluidcommunication with the wellbore 14 external to the dampener 32, so thatwell fluid is in the cavity. Thus, the cavity 38 could be pressurebalanced with the wellbore 14 surrounding the dampener 32. Again, thesize, shape and position of the cavity 38 may be adjusted to target aparticular pressure wave frequency band. As with the constructiondepicted in FIG. 3, the interior and/or exterior surfaces 37, 39 of thematerial 34 may be smooth, and/or may be provided with scallops,crenellations, fingers, peaks and valleys, recesses, projections, etc.

[0039] Referring additionally now to FIG. 6, another pressure wavedampener 46 is representatively illustrated. The dampener 46 may be usedfor the dampener 30 in the method 10. However, it should be understoodthat the dampener 46 may be used in other methods, without departingfrom the principles of the invention.

[0040] The dampener 46 includes an enclosed volume 48 within a housing50 having multiple openings 52 through a sidewall thereof. Flowpaths 54provide fluid communication between the volume 48 and the openings 52.When the dampener 46 is positioned in a well, such as that depicted inFIG. 1, the openings 52 and flowpaths 54 provide fluid communicationbetween the volume 48 and the wellbore 14 external to the dampener.

[0041] The dampener 46 is similar in many respects to a device known tothose skilled in the acoustic damping art as a Helmholtz resonator. AHelmholtz resonator cancels sound waves by generating sound waves out ofphase. The sound waves enter the resonator openings, travel through theflowpaths to the volume, and are reflected back out of phase.

[0042] The Helmholtz resonator is particularly useful in targeting arelatively narrow frequency band of sound waves at which it resonates.The approximate resonant frequency of a Helmholtz resonator is given bythe following formula: f=c/2π(A/LV)^(1/2), in which c is the speed ofsound, A is the area of the openings, L is the length of the flowpathsand V is the internal volume. It is believed that the same formula wouldapproximate the resonant frequency of the dampener 46 depicted in FIG.6.

[0043] Several modifications may be made to the dampener 46 to increasethe frequency band at which it is effective to dampen the pressurewaves. For example, the flowpaths 54 may be perforated as shown at 56 tothereby provide multiple flowpath lengths between the openings 52 andthe volume 48, and to add viscous damping. As another example, apressure wave absorbent material 58 may be positioned in the volume 48to add viscous damping.

[0044] Referring additionally now to FIG. 7, another pressure wavedampener 60 is representatively illustrated. The dampener 60 may be usedfor the dampener 30 in the method 10. However, it should be understoodthat the dampener 60 may be used in other methods, without departingfrom the principles of the invention.

[0045] The dampener 60 is somewhat similar to the dampener 46 describedabove, in that it includes an internal chamber 62 and multiple openings64 providing fluid communication between the internal chamber and thewell exterior to the dampener. The openings 64 are formed through asidewall 66 separating the chamber 62 from the well exterior to thedampener 60. However, the dampener 60 does not have elongated flowpathsbetween the openings 64 and the chamber 62.

[0046] Preferably, the openings 64 have a combined area which isapproximately 30% to 60% of the surface area of the sidewall 66. Thisconfiguration uses viscous damping of the pressure waves travelingthrough the sidewall 66 to damp the pressure waves. By adjusting thesize, shape, number and positioning of the openings 64, and the size andshape of the chamber 62, the frequency band at which maximum pressurewave attenuation is achieved may be altered as desired. In addition,pressure wave absorbent material 68 may be positioned in the chamber 62.

[0047] Referring additionally now to FIG. 8, another pressure wavedampener 70 is representatively illustrated. The dampener 70 may be usedfor the dampener 30 in the method 10, except that the dampener 70 iscombined with a perforating gun 72. Of course, the dampener 70 may beused in other methods, without departing from the principles of theinvention.

[0048] An internal volume 74 is formed in the gun 72. Flowpaths 76extend into the volume 74 from a sidewall 78 of the gun 72. It will bereadily appreciated that, when the gun 72 is detonated, openings (notshown) will be formed by perforators 80 (explosive shaped charges)through the sidewall 78. At that point, the gun 72 will be very similarto the dampener 46 depicted in FIG. 6, in that the openings andflowpaths 76 will provide fluid communication between the volume 74 andthe wellbore external to the dampener 70.

[0049] Referring additionally now to FIG. 9, another pressure wavedampener 82 is representatively illustrated. The dampener 82 may be usedfor the dampener 30 in the method 10. However, it should be understoodthat the dampener 82 may be used in other methods, without departingfrom the principles of the invention.

[0050] The dampener 82 acts by viscously damping the pressure wavestraveling through an annulus 84 formed between the wellbore 14 and thetubing string 12. The dampener 82 includes whiskers or fibers 86extending outwardly from a central axially extending mandrel 88.Preferably, the fibers 86 contact the wellbore 14, in which case thefibers may be deployed after the dampener 82 is conveyed into the well,for example, by removing a shroud (not shown) initially constraining thefibers. Removal of the shroud enables the fibers 86 to extend outwardinto contact with the wellbore 14.

[0051] The fibers 86 may be made of any material, including steel, othermetals, plastics, composites, etc. The fibers 86 may be made of a phasechange alloy, in which case the pressure waves traveling through thefibers induce strain in the fibers, which causes the fibers to changephase and thereby absorb increased energy from the pressure waves.

[0052] In FIG. 10, the dampener 82 is depicted from a side view apartfrom the wellbore 14. In this view it may be clearly seen that thefibers 86 have a density which increases in the downward direction. Itwill be readily appreciated that the fibers 86 also have a density whichincreases in the radially inward direction as well. This varied densityaids in impedance matching to the fluid in the well, decreasing theamplitude of pressure waves reflected from the dampener 82.

[0053] Referring additionally now to FIG. 11, another method 90embodying principles of the invention is representatively illustrated.Elements depicted in FIG. 11 which are similar to elements previouslydescribed are indicated in FIG. 11 using the same reference numbers.

[0054] In the method 90, the perforating gun 20 is separated from theequipment, such as a well screen 92 and packer 16, for which protectionis desired. For example, the perforating gun 20 may be separatelyconveyed into the wellbore 14 (such as by wireline or tubing conveyance)and anchored therein using a gun hanger 94. Alternatively, theperforating gun 20, hanger 94 and the remainder of a tubing string 96may be conveyed together into the wellbore 14, the hanger 94 set in thecasing 24, the tubing string 96 above the hanger disconnected and raisedin the wellbore 14, and the packer 16 set in the casing to anchor thetubing string.

[0055] Although the packer 16 and screen 92 are physically separatedfrom the perforating gun 20, they are still subject to damage due topressure waves generated by detonation of the perforating gun 20. Any ofthe dampeners 32, 46, 60, 70, 82 described above may be used in themethod 90 to dampen these pressure waves. However, the method 90 usesanother pressure wave dampener 98.

[0056] The dampener 98 is constructed with a relatively thin outer wallor shroud 100 which is intentionally designed to deform when itencounters the pressure waves generated by the perforating gun 20. Thisdeformation of the shroud 100 absorbs energy from the pressure waves.The shroud 100 may deform plastically and/or elastically in response tothe pressure waves. It is preferred that the shroud 100 deformplastically in order to absorb a greater amount of energy.

[0057] Referring additionally now to FIG. 12, another method 102embodying principles of the invention is representatively illustrated.Elements depicted in FIG. 12 which are similar to elements previouslydescribed are indicated in FIG. 12 using the same reference numbers.

[0058] The method 102 is substantially similar to the method 90described above. However, instead of the dampener 98, the method 102uses a pressure wave dampener 104 which has whiskers or fibers 106extending inwardly from an outer shroud 108. The fibers 106 may besimilar to the fibers 86 described above.

[0059] The dampener 104 viscously dampens the pressure waves as theytravel through the fibers 106. This reduces the transmission andreflection of the pressure waves in the wellbore 14, thereby protectingthe packer 16 and screen 92 from damage due to pressure differentialscreated by the pressure waves.

[0060] Of course, a person skilled in the art would, upon a carefulconsideration of the above description of representative embodiments ofthe invention, readily appreciate that many modifications, additions,substitutions, deletions, and other changes may be made to thesespecific embodiments, and such changes are contemplated by theprinciples of the present invention. Accordingly, the foregoing detaileddescription is to be clearly understood as being given by way ofillustration and example only, the spirit and scope of the presentinvention being limited solely by the appended claims and theirequivalents.

What is claimed is:
 1. A perforating system for a subterranean well,comprising: a perforating gun positioned in the well; and a fluidpressure wave dampener positioned in the well, the dampener dampingpressure waves generated by detonation of the perforating gun.
 2. Theperforating system according to claim 1, wherein the dampener includes apressure wave absorbent material.
 3. The perforating system according toclaim 2, wherein the pressure wave absorbent material is a porousmaterial.
 4. The perforating system according to claim 2, wherein thepressure wave absorbent material is a fibrous material.
 5. Theperforating system according to claim 2, wherein the pressure waveabsorbent material is steel wool.
 6. The perforating system according toclaim 2, wherein the pressure wave absorbent material is mineral wool.7. The perforating system according to claim 2, wherein the pressurewave absorbent material dampens pressure waves by viscous damping offluid flowing through the pressure wave absorbent material.
 8. Theperforating system according to claim 2, further comprising a hollowcavity formed within the pressure wave absorbent material.
 9. Theperforating system according to claim 8, wherein the hollow cavity has apredetermined size which tunes the system to absorb a desired pressurewave frequency band.
 10. The perforating system according to claim 8,wherein the pressure wave absorbent material is generally annularshaped, an exterior surface of the pressure wave absorbent materialbeing in contact with fluid in the well exterior to the dampener, and aninterior surface of the pressure wave absorbent material being incontact with the cavity.
 11. The perforating system according to claim8, wherein the cavity is substantially filled with liquid.
 12. Theperforating system according to claim 11, wherein the liquid is wellfluid.
 13. The perforating system according to claim 11, wherein animpermeable flexible membrane separates the pressure wave absorbentmaterial from the cavity.
 14. The perforating system according to claim2, wherein the dampener is interconnected in a tubular string positionedin the well, a flow passage of the tubular string extending through thedampener.
 15. The perforating system according to claim 14, wherein theflow passage is isolated from the pressure wave absorbent material. 16.The perforating system according to claim 1, wherein the dampenerincludes an enclosed volume V, at least one opening having an area A, atleast one flowpath having a length L and extending between the openingand the volume, the flowpath providing fluid communication between thevolume and the well exterior to the dampener.
 17. The perforating systemaccording to claim 16, wherein the dampener has a resonant frequency fapproximately given by the formula: f c/2π(A/LV)^(1/2), in which c isthe speed of sound.
 18. The perforating system according to claim 17,wherein the dampener has maximum pressure wave attenuation at theresonant frequency.
 19. The perforating system according to claim 16,wherein the dampener further includes a pressure wave absorbent materialpositioned in the enclosed volume.
 20. The perforating system accordingto claim 16, wherein the flowpath is perforated, thereby providingmultiple flowpath lengths between the opening and the enclosed volume.21. The perforating system according to claim 16, wherein the dampeneris formed as part of the perforating gun.
 22. The perforating systemaccording to claim 16, wherein a perforator is positioned within theflowpath.
 23. The perforating system according to claim 16, wherein theopening is formed by a perforator of the perforating gun.
 24. Theperforating system according to claim 16, wherein the opening is formedwhen the perforating gun is detonated.
 25. The perforating systemaccording to claim 1, wherein the dampener includes an internal chamberand multiple openings providing fluid communication between the internalchamber and the well exterior to the dampener.
 26. The perforatingsystem according to claim 25, wherein the dampener further includes apressure wave absorbent material positioned within the chamber.
 27. Theperforating system according to claim 25, wherein the openings areformed through a sidewall of the dampener separating the chamber fromthe well exterior to the dampener, and wherein the openings compriseapproximately 30% to approximately 60% of the sidewall surface area. 28.The perforating system according to claim 1, wherein the dampenerincludes multiple fibers extending through fluid in the well, the fibersviscously damping the pressure waves passing through the dampener. 29.The perforating system according to claim 28, wherein the fibers extendoutwardly from an axially extending mandrel of the dampener.
 30. Theperforating system according to claim 29, wherein the fibers extendbetween the mandrel and a wellbore of the well.
 31. The perforatingsystem according to claim 28, wherein the fibers contact a wellbore ofthe well.
 32. The perforating system according to claim 28, wherein thefibers extend inwardly from an outer shroud of the dampener.
 33. Theperforating system according to claim 28, wherein the fibers have adensity which varies axially relative to a wellbore of the well.
 34. Theperforating system according to claim 28, wherein the fibers have adensity which varies radially relative to a wellbore of the well. 35.The perforating system according to claim 28, wherein the fibers aremade of a phase change alloy which changes phase in response to straininduced in the fibers by the pressure waves.
 36. The perforating systemaccording to claim 28, wherein the dampener is separated from theperforating gun when the perforating gun is detonated.
 37. Theperforating system according to claim 28, wherein the dampener isseparately anchored in the well from the perforating gun when theperforating gun is detonated.
 38. The perforating system according toclaim 1, wherein the dampener deforms to thereby absorb energy from thepressure waves.
 39. The perforating system according to claim 38,wherein the dampener is separated from the perforating gun when theperforating gun is detonated.
 40. The perforating system according toclaim 38, wherein the dampener is separately anchored in the well fromthe perforating gun when the perforating gun is detonated.
 41. Theperforating system according to claim 1, wherein the dampener isseparated from the perforating gun when the perforating gun isdetonated.
 42. The perforating system according to claim 1, wherein thedampener is separately anchored in the well from the perforating gunwhen the perforating gun is detonated.
 43. The perforating systemaccording to claim 1, wherein the dampener is interconnected between theperforating gun and a well screen in a tubular string.
 44. Theperforating system according to claim 1, wherein the dampener isinterconnected between the perforating gun and a packer in a tubularstring.
 45. The perforating system according to claim 1, wherein thedampener is positioned at a location of approximate maximum pressurewave velocity in the well.
 46. The perforating system according to claim1, wherein the dampener is positioned at a location of approximateminimum pressure wave velocity in the well.
 47. The perforating systemaccording to claim 1, wherein the dampener is tuned to attenuate thepressure waves having a predetermined approximate wavelength.
 48. Theperforating system according to claim 47, wherein the dampener ispositioned approximately one-fourth of the wavelength from a bottom ofthe well.
 49. The perforating system according to claim 47, furthercomprising a plug set in the well below the perforating gun, and whereinthe dampener is positioned approximately one-fourth of the wavelengthfrom the plug.
 50. The perforating system according to claim 47, furthercomprising a packer set in the well above the perforating gun, andwherein the dampener is positioned approximately one-fourth of thewavelength from the packer.
 51. The perforating system according toclaim 1, wherein the dampener is positioned approximately one-fourth ofa distance between a top of the perforating gun and a bottom of thewell.
 52. The perforating system according to claim 1, furthercomprising a packer, and wherein the dampener is positionedapproximately one-fourth of a distance between the packer and a bottomof the well.
 53. The perforating system according to claim 1, furthercomprising a packer, and wherein the dampener is positioned proximatethe packer.
 54. The perforating system according to claim 1, wherein thedampener is positioned proximate a top of the perforating gun.
 55. Theperforating system according to claim 1, wherein the dampener ispositioned proximate a bottom of the well.
 56. A method of dampingpressure waves in a subterranean well, the method comprising the stepsof: providing a fluid pressure wave dampener; positioning the dampenerin the well; generating the pressure waves in the well; and damping thepressure waves with the dampener.
 57. The method according to claim 56,wherein the providing step further comprises providing the dampenerincluding a pressure wave absorbent material.
 58. The method accordingto claim 57, wherein in the providing step, the pressure wave absorbentmaterial is a porous material.
 59. The method according to claim 57,wherein in the providing step, the pressure wave absorbent material is afibrous material.
 60. The method according to claim 57, wherein thedamping step further comprises viscously damping the pressure wavesflowing through the absorbent material.
 61. The method according toclaim 57, wherein the providing step further comprises forming a hollowcavity within the pressure wave absorbent material.
 62. The methodaccording to claim 61, wherein in the forming step, the hollow cavity isformed to a predetermined size which tunes the system to absorb adesired pressure wave frequency band.
 63. The method according to claim61, wherein in the providing step, the pressure wave absorbent materialis generally annular shaped, an exterior surface of the pressure waveabsorbent material being in contact with fluid in the well exterior tothe dampener, and an interior surface of the pressure wave absorbentmaterial being in contact with the cavity.
 64. The method according toclaim 61, wherein in the providing step further comprises substantiallyfilling the cavity with liquid.
 65. The method according to claim 61,wherein the providing step further comprises separating the pressurewave absorbent material from the cavity with an impermeable flexiblemembrane.
 66. The method according to claim 57, further comprising thestep of interconnecting the dampener in a tubular string positioned inthe well, a flow passage of the tubular string extending through thedampener.
 67. The method according to claim 66, further comprising thestep of isolating the flow passage from the pressure wave absorbentmaterial.
 68. The method according to claim 56, wherein in the providingstep, the dampener includes an enclosed volume V, at least one openinghaving an area A, at least one flowpath having a length L and extendingbetween the opening and the volume, the flowpath providing fluidcommunication between the volume and the well exterior to the dampener.69. The method according to claim 68, wherein in the providing step, thedampener has a resonant frequency f approximately given by the formula:f=c/2π(A/LV)^(1/2), in which c is the speed of sound.
 70. The methodaccording to claim 69, wherein in the damping step, the dampener hasmaximum pressure wave attenuation at the resonant frequency.
 71. Themethod according to claim 68, wherein the providing step furthercomprises positioning a pressure wave absorbent material in the enclosedvolume.
 72. The method according to claim 68, wherein in the providingstep, the flowpath is perforated, thereby providing multiple flowpathlengths between the opening and the enclosed volume.
 73. The methodaccording to claim 68, wherein the providing step further comprisesforming the dampener as part of a perforating gun.
 74. The methodaccording to claim 68, wherein the providing step further comprisespositioning a perforator within the flowpath.
 75. The method accordingto claim 68, wherein the providing step further comprises forming theopening by a perforator.
 76. The method according to claim 68, whereinthe providing step further comprises forming the opening when aperforating gun is detonated.
 77. The method according to claim 56,wherein in the providing step, the dampener includes an internal chamberand multiple openings providing fluid communication between the internalchamber and the well exterior to the dampener.
 78. The method accordingto claim 77, wherein the providing step further comprises positioning apressure wave absorbent material within the chamber.
 79. The methodaccording to claim 77, wherein the providing step further comprisesforming the openings through a sidewall of the dampener separating thechamber from the well exterior to the dampener, and wherein the openingscomprise approximately 30% to approximately 60% of the sidewall surfacearea.
 80. The method according to claim 56, wherein in the providingstep, the dampener includes multiple fibers extending through fluid inthe well, and wherein the damping step further comprises viscouslydamping the pressure waves passing through the fibers.
 81. The methodaccording to claim 80, wherein in the providing step, the fibers extendoutwardly from an axially extending mandrel of the dampener.
 82. Themethod according to claim 80, wherein in the providing step, the fibersextend between the mandrel and a wellbore of the well.
 83. The methodaccording to claim 80, wherein the positioning step further comprisescontacting the fibers with a wellbore of the well.
 84. The methodaccording to claim 80, wherein the positioning step further comprisesextending the fibers inwardly from an outer shroud of the dampener. 85.The method according to claim 80, wherein the providing step furthercomprises varying a density of the fibers axially relative to a wellboreof the well.
 86. The method according to claim 80, wherein the providingstep further comprises varying a density of the fibers radially relativeto a wellbore of the well.
 87. The method according to claim 80, whereinthe providing step further comprises making the fibers out of a phasechange alloy which changes phase in response to strain induced in thefibers by the pressure waves.
 88. The method according to claim 80,wherein the positioning step further comprises separating the dampenerfrom a perforating gun in the well, wherein the generating step furthercomprises detonating the perforating gun, and wherein the damping stepfurther comprises damping the pressure waves generated when theperforating gun is detonated.
 89. The method according to claim 80,wherein the positioning step further comprises separately anchoring thedampener in the well from a perforating gun prior to the generatingstep.
 90. The method according to claim 56, wherein the damping stepfurther comprises deforming the dampener to thereby absorb energy fromthe pressure waves.
 91. The method according to claim 90, wherein thepositioning step further comprises separating the dampener from aperforating gun in the well prior to the generating step.
 92. The methodaccording to claim 90, wherein the positioning step further comprisesseparately anchoring the dampener in the well from a perforating gunprior to detonating the perforating gun.
 93. The method according toclaim 56, wherein the positioning step further comprises separating thedampener from a perforating gun prior to detonating the perforating gun.94. The method according to claim 56, wherein the positioning stepfurther comprises separately anchoring the dampener in the well from aperforating gun prior to detonating the perforating gun.
 95. The methodaccording to claim 56, wherein the positioning step further comprisesinterconnecting the dampener between a perforating gun and a well screenin a tubular string.
 96. The method according to claim 56, wherein thepositioning step further comprises interconnecting the dampener betweena perforating gun and a packer in a tubular string.
 97. The methodaccording to claim 56, wherein the positioning step further comprisespositioning the dampener at a location of approximate maximum pressurewave velocity in the well.
 98. The method according to claim 56, whereinthe positioning step further comprises positioning the dampener at alocation of approximate minimum pressure wave velocity in the well. 99.The method according to claim 56, wherein the providing step furthercomprises tuning the dampener to attenuate the pressure waves having apredetermined approximate wavelength.
 100. The method according to claim99, wherein the positioning step further comprises positioning thedampener approximately one-fourth of the wavelength from a bottom of thewell.
 101. The method according to claim 99, further comprising the stepof setting a plug in the well below a perforating gun, and wherein thepositioning step further comprises positioning the dampenerapproximately one-fourth of the wavelength from the plug.
 102. Themethod according to claim 99, further comprising the step of setting apacker in the well above a perforating gun, and wherein the positioningstep further comprises positioning the dampener approximately one-fourthof the wavelength from the packer.
 103. The method according to claim56, wherein the positioning step further comprises positioning thedampener approximately one-fourth of a distance between a top of aperforating gun and a bottom of the well.
 104. The method according toclaim 56, wherein the positioning step further comprises positioning thedampener approximately one-fourth of a distance between the packer and abottom of the well.
 105. The method according to claim 56, wherein thepositioning step further comprises positioning the dampener proximate apacker in the well.
 106. The method according to claim 56, wherein thepositioning step further comprises positioning the dampener proximate atop of a perforating gun.
 107. The method according to claim 56, whereinthe positioning step further comprises positioning the dampenerproximate a bottom of the well.
 108. The method according to claim 56,wherein the providing step further comprises forming recesses on asurface of a pressure wave absorbent material of the dampener.
 109. Themethod according to claim 108, wherein the forming step furthercomprises forming scallops on the material surface.
 110. The methodaccording to claim 108, wherein the forming step further comprisesforming crenellations on the material surface.
 111. The method accordingto claim 56, wherein the providing step further comprises formingprojections on a surface of a pressure wave absorbent material of thedampener.
 112. The method according to claim 111, wherein the formingstep further comprises forming fingers on the material surface.
 113. Themethod according to claim 111, wherein the forming step furthercomprises forming peaks on the material surface.
 114. The methodaccording to claim 56, wherein the pressure wave generating step furthercomprises performing a formation fracturing operation in the well. 115.The method according to claim 56, wherein the pressure wave generatingstep further comprises setting a packer in the well.
 116. The methodaccording to claim 56, wherein the pressure wave generating step furthercomprises performing a casing repair operation in the well.
 117. Themethod according to claim 56, wherein the pressure wave generating stepfurther comprises detonating a perforating gun in the well.